184 Drew .— The Reproduction and early Development of 
In from two to three days after inoculation with pieces of the mature 
reproductive areas, the solution became slightly clouded ; this cloudiness 
was more noticeable in the focus of the light and near the surface of the 
liquid. On examination, a drop of water showed a number of flagellated 
gametes, about -003 mm. in diameter (Fig. 5, b\ spherical in shape, and 
consisting of granular protoplasm which usually showed a minute dark 
spot in the region opposite the attachment of the flagella. Each gamete 
has two flagella, the longer measuring about -015 mm., and the shorter 
about -004 mm. ; the longer flagellum shows an active wriggling motion, 
whilst the shorter is more sluggish, and is usually held straight and motion¬ 
less. Both flagella are inserted close together. The movement of the 
gametes is not very rapid, and appears to consist partly in revolution round 
a centre situated a little outside the centre of the body of the gamete, and 
partly in progression in the direction of the longer flagellum. 
When observing the actual process of rupture of the gametangia, it 
was seen that the gametes were liberated as spherical non-flagellated bodies, 
containing a faint trace of a yellowish colouring matter (Fig. 4). At first 
these bodies are found embedded in the mucilaginous substance secreted by 
the cells of the lamina, and whilst in this position appear to lose their 
colouring matter and then protrude the flagella. Numbers of these non- 
flagellated bodies can be found by carefully removing the mucilage from 
the surface of the reproductive areas, after they have been standing in the 
nutrient solution for a few days. After the protrusion of the flagella the 
gametes soon escape from the surrounding mucilage and swim towards 
the light. 
On examining the free swimming gametes obtained in culture experi¬ 
ments, forms were found in which two gametes were partially fused ; some 
were in contact at the points of origin of the flagella, and others showed 
more complete fusion, but in these the flagella had disappeared (Fig. 5, 
c and d). 
Observation of the actual process of conjugation presents considerable 
difficulties. Owing to the minute size of the gametes, it is necessary 
to use a inch objective, or a lens of similar resolving power, if satis¬ 
factory results are to be obtained. If the gametes are in a hanging drop or 
in a sufficiently thick film of water to approximate to natural conditions, it is 
found that they soon move out of focus, or out of the field of view, so that 
it is difficult to keep any one gamete under observation for a prolonged 
period. 
Before conjugation, two gametes approach one another, and the longer 
flagella often become entangled. As they draw nearer, the long flagellum 
of each gamete partially embraces the body of the other, and while in this 
position both gametes appear to slowly revolve round a common centre. 
Contact between the bodies of the gametes first takes place at the point of 
